/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.wicketstuff.minis.model;

import java.util.Collection;

import org.apache.wicket.model.IModel;
import org.apache.wicket.util.string.Strings;

/**
 * Model of whether the object of the dependent model is empty or null.
 *
 * @param <W>
 *            type of the dependent model
 */
public class IsEmptyOrNullModel<W> extends LoadableDetachableDependentModel<Boolean, W>
{

	/**
	 * Constructor.
	 * 
	 * @param dependentModel
	 *            non-null collection model this model depends on
	 */
	public IsEmptyOrNullModel(IModel<W> dependentModel)
	{
		super(dependentModel);
	}

	@Override
	protected Boolean load()
	{
		boolean empty = true;
		W dependentValue = getDependentModel().getObject();
		if (dependentValue instanceof Collection)
		{
			empty = ((Collection<?>)dependentValue).isEmpty();
		}
		else if (dependentValue instanceof CharSequence)
		{
			empty = Strings.isEmpty((CharSequence)dependentValue);
		}
		else
		{
			empty = dependentValue == null;
		}
		return empty;
	}

}
